Means for pressurising liquids



May 9, 1967 D. GREEN MEANS FOR PRESSURISING LIQUIDS V I??? 'IV FiledJan. 29, 1965 United States Patent 3,318,256 MEANS FOR PRESSURISINGLIQUIDS Derek Green, St. Annes, England, assignor to United KingdomAtomic Energy Authority, London, England Filed Jan. 29, 1965, Ser. No.429,104

Claims priority, application Great Britain, Feb. 20, 1964,

7,238/ 64 1 Claim. (Cl. 103178) This invention relates to means forpressurising liquids.

Means for pressurising liquids has one application in hydrostaticextrusion apparatus, in which a work piece is forced through a diemounted at the end of a pressure container by liquid pressure actingdirectly on the workpiece. The pressure is normally generated by aplunger and barrel assembly but because the plunger has no physicalcontact with the workpiece and because the workpiece is side supportedby the liquid in passage through the die, bending forces aresubstantially avoided thus enabling long and slender workpieces such aswire to be extruded. Furthermore, as a coating of the liquid is passedthrough the die with the workpiece thus providing lubricant and as thereis no physical contact of the workpiece with the wall of the pressurecontainer, frictional resistance to extrusion is also considerablyreduced. The production of long and slender articles by the apparatus isfacilitated if the pressure container is horizontally disposed so thatthe extrusion takes place horizontally through a die in the end of thecontainer. The plunger and barrel assembly are preferably verticallymounted being interconnected with the pressure container by a duct, theplunger acting downwardly to pressurise the liquid in the container.However, because of the high pressure involved making it preferable toavoid weakening the wall of the barrel or container by penetrations, itbecomes necessary to remove the plunger to replenish liquid lost aslubricant to the workpiece and not only is this an expensive timeconsuming operation but it is made more complex by the verticaldisposition of the plunger. The lack of penetrations in the wall of thebarrel also makes diflicult the bleeding of air entrapped duringassembly from the underside of the plunger. In conventional apparatusthe gland sealing means for the plunger can include an embracing mitresealing ring, that is to say, an annular member having a right angletriangular shaped cross section; the base of the triangle defines thewidth of the member and is the side which contacts the wall of thebarrel, the side normal to the base defines the depth of the face of thering which face is presented to the pressurised fluid, and thehypotenuse defines an oblique face which in use abuts a a cooperatingoblique annular face formed on the plunger so that when the plunger ismoved on a liquid pressurising stroke the annular ring is urged againstthe oblique annular face formed on the plunger causing the ring toexpand radially outwardly to engage the wall of the barrel in sealingmanner. Hereinafter the term mitre sealing ring is intended to mean asealing ring of this kind. Initial sealing is effected by a rubber Oring which is in front of the mitre sealing ring on a pressurisingstroke and which serves to prevent liquid pressure escaping past themitre sealing ring at the commencement of the pressurising stroke beforethe mitre sealing ring has expanded radially sufficiently to provide asatisfactory seal and also to prevent the ingress of air on the returnstroke. However, the rubber O ring is subject to damage and/ordisplacement from its location on the plunger as a result of the returnmotion of the plunger on the non-pressurising stroke because the thrustrequired to overcome the frictional resistance between the mitre "icegland sealing ring and the barrel wall is applied through the rubber Oring.

According to the invention, means for pressurising liquids comprises abarrel having a cylindrical bore, a loose fitting plunger entered intothe bore of the barrel, a cylindrical body member movable in the bore ofthe barrel, means sealing circumferentially between the cylindrical bodymember and the bore of the barrel, coupling means retaining the bodymember in front of the plunger when the plunger is moved in the barrel,said coupling means having a lost motion characteristic, such that theplunger is movable longitudinally in the barrel between limits relativeto the body member, a duct extending from end to end of the body member,sealing means operable to close said duct when the plunger is in end toend abutment with the body member on a liquid pressurising stroke of theplunger, said sealing means being inoperable such that the duct is openwhen the plunger parts from the cylindrical body member on the returnnonpressurising stroke of the plunger by an amount governed by the lostmotion characteristic of the coupling means between the cylindrical bodymember and the plunger.

The invention provides that on the return non-pressurising stroke, whenthe body member and plunger part sufiiciently to open the duct,entrapped air is expelled from the underside of the plunger via saidduct.

A reservoir for liquid is provided outside the barrel for feeding liquidto the annular space defined between the loose fitting plunger and thebore of the barrel so on the return or non-pressurising stroke of theplunger and body member, liquid can flow through the annular space andthrough the duct in the body member to replenish the liquid in thebarrel. The means sealing circumferentially between the body member andthe bore of the barrel comprises a mitre sealing ring held between anexternal oblique face on the body member and a thrust ring fixed on thebody member, a rubber sealing ring being disposed around the thrust ringin sealing contact with the bore of the barrel.

A liquid pressurising plunger and barrel assembly embodying theinvention, for application for example to hydrostatic extrusionapparatus, will now be described, by way of example with reference tothe accompanying drawings wherein:

FIGURES 1, 2 and 3 are fragmentary views in section showing the plungerand barrel assembly in three operative positions, FIGURE 1 showing apart of the assembly in section whilst FIGURES 2 and 3 show that part inelevation.

In the drawing there is shown a gland sealing assembly I mounted on theplunger 2 in the barrel 3. The gland seal assembly comprises asubstantially cylindrical body member 4 slidable in the barrel andretained on the plunger by a screw bolt 5. Circumferential sealing ofthe body member 4 with the wall of the barrel is effected by a rubber Oring 6 and a nylon mitre backing ring 7. The ring 7 is located betweenan oblique face on the body member 4 and a stepped thrust ring 8 whichis retained on the body member by a nut 9 and is sealed to the bodymember by a second rubber O ring 10 and a mitre backing ring 11. Acentral bore through which the bolt extends to engage the plungertogether with the shank of the bolt defines an annular duct 12 and atthe mouth of the duct 12 adjacent the plunger, a mitre backing ring 13serves to seal the duct when the bodymember 4 is in abutment with theplunger. The bolt 5 has a head 14 with a groove 15 and is disposed sothat the plunger 2 is capable of moving axially into or out of abutmentwith the body member. When the plunger 2 is out of abutment with thebody member and in abutment with the head of the bolt as shown inFIGURES 2 and 3 the groove 15 and body member 4 define a duct whichcoincides with the annular duct 12. The plunger 2 and bore of the barrel3 are of diameters suitable to define an annular duct 16 which extendsto a reservoir 17.

In the construction of hydrostatic extrusion apparatus of which thedescribed plunger and barrel assembly forms a part, the barrel ismounted with its longitudinal axis vertically disposed and in FIGURE 1the plunger is shown on a downward liquid pressurising stroke asindicated by the arrow designated A so that the plunger 2 is urged intoabutment with the body member 4 to seal the head of the plunger againstleakage of pressure.

In FIGURE 2 the plunger is shown to have commenced the upward returnstroke as indicated by the arrow A so that, because of the frictionalresistance to movement of the gland seals, the plunger is drawn out ofabutment with the body member 4. The ducts 15, 12 interconnect the endsof the seal assembly so that any air entrapped in the liquid is ejectedto the reservoir 17 via the annular duct 16 as indicated by the arrowsdesignated B.

In FIGURE 3 the plunger 2 is shown continuing its upward return strokeas indicated by the arrow A and liquid is able to flow from thereservoir 17 as indicated by the arrows designated C to replenish theinterior of the barrel on the pressurising side of the seal assembly viathe ducts 12, 15 thereby compensating for liquid lost as lubricant forthe workpiece in passage through the die and also filling the voidageresulting from the expulsion of air from the liquid. During the upwardreturn stroke the frictional resistance to movement of the mitre backingring in contact with the wall of the barrel is overcome when the head 14of the bolt abuts the body member. The thrust is taken via the thrustring 8 instead of the O ring 6 as in the previously known equipment thusavoiding consequential damage to the O ring.

I claim:

Means for pressurising liquids comprising a barrel having a cylindricalbore, a loose fitting plunger entered into the bore of the barrel, acylindrical body member movable in the bore of the barrel, sealingmean-s sealing circumferentially between the cylindrical body member andthe bore of the barrel, said sealing means comprising a mitre sealingring held between an oblique face on the body member and a thrust ringfixed on the body member, a rubber sealing ring being disposed aroundthe thrust ring in sealing contact with the bore of the barrel, couplingmeans retaining the body member in front of the plunger when the plungeris moved in the barrel, said coupling means having a lost motioncharacteristic such that the plunger is movable longitudinally in thebarrel between limits relative to the cylindrical body member, a ductextending from end to end of the body member, duct sealing meansoperable to close said duct when the plunger is in end to end abutmentwith the body member on a liquid pressurising stroke of the plunger,said duct having a conical mouth opening to face the adjacent end faceof the plunger, said duct sealing means comprising a mitre sealing ringhaving a conical face engaging with the conical mouth of the duct and aflat annular end face engaging to seal with the end face of the plungerwhen the plunger is in end to end abutment with the body member on aliquid pressurising stroke of the plunger, the fiat annular end face ofthe mitre sealing ring being disengaged from sealing with the end faceof the plunger, such that the duct is open when the plunger parts fromthe cylindrical body member on a return non-pressurising stroke of theplunger by an amount governed by the lost motion characteristic of thecoupling means between the cylindrical body member and the plunger, areservoir for liquid being provided in connection with the barrel forfeeding of liquid into the bore of the barrel so that on the returnnon-pressurising stroke of the plunger liquid can flow between theplunger and the bore of the barrel and then through the duct in the bodymember to replenish liquid in the bore of the barrel below thecylindrical body member.

References Cited by the Examiner UNITED STATES PATENTS 2,462,586 2/1949Whittingham 277188 2,739,855 3/1956 Bruning 277l88 2,894,665 7/1959Zerlin 103-178 2,931,313 5/1960 Hughes 103-203 FOREIGN PATENTS 740,1141/1931 France. 622,824 7/1961 Italy.

DONLEY I. STOCKING, Primary Examiner.

W. L. FREEH, Assistant Examiner.

